Airmar 2018 part 2: Ultrasonic and EM speedo mysteries unraveled, plus new UDST800

Airmar_UDST800_ultrasonic_triducer_for_real_2-2018_cPanbo.jpgAirmar’s newly announced UDST800 Ultrasonic Smart Triducer is real! I’ve held one in my freckly hand and even installed it on Gizmo. The reality of a new product would not normally be news, but the history of Airmar’s high tech ultrasonic and electromagnetic speed sensors has frustrated boaters wanting the promised precise and reliable Speed through the Water results, which should be many boaters, I think…

Airmar_DST900-EM_and_ultrasonic_ST900_never_shipped_cPanbo.jpgTo be brutally frank, neither of the Airmar products described above ever materialized as presented, and the same is true for the Ultrasonic DST900 that Kees Verruijt enthusiastically photographed and explained in 2012. In fact, as he mentions, this odd situation started years earlier.

In Oct. 2009 Dan Corcoran’s great review of the Airmar CS4500 Ultrasonic speedo kicked off a discussion about how the high value of accurate STW (sometimes just called Speed, but definitely different from the Speed over Ground delivered by GPS). Sailors crave it for precise calculation of True Wind relative to water, but so do power cruisers for better miles-per-gallon fuel calculations. Accurate STW is also key to meaningful set and drift calculations.

There’s also talk in an old entry about how much better the ultrasonic technology would be as a “smart” transducer able to send data directly to NMEA 2000 networks (or to NMEA 0183). And one Panbo commenter came up with a still-live link to the Airmar DST900-EM — “Available Q3 2009” — while another pasted in an Airmar tech support note about an ultrasonic NMEA 2000 triducer about to come out as the DST900-CL (and those revelations led to a discussion about how electromagnetic speed sensing might compare to ultrasonic).

So in 2009, and again in 2012, there seemed to be at least a hard core crowd ready and willing to spend extra money to say goodbye to their paddlewheel speed sensor in favor of more accurate and reliable technology. They never got a chance to pull out their wallets. What happened?

I do not know why Airmar made several false starts in this area — there’s no upside I can think of — but I can theorize. As mentioned in my Part 1 entry about Airmar’s certified installer program, the company mostly works with OEM’s, not retail customers, and maybe trial balloons are more normal in that environment. It’s also an engineer-run company, so maybe testing trumped marketing. Perhaps, above all, the market for premium speed sensors is small, while Airmar has been relentlessly pushing out into other markets while also driving the CHIRP fishfinder revolution.

And none of this matters much now, except to hopefully clear the air and set the stage before we discuss Airmar ultrasonic and electromagnetic speed technology that really, really does exist.

DX900+ MultiLog

Airmar_DX900+_Sail_Pittman_aPanbo.jpgFirst, let’s consider the Airmar DX900+ MultiLog that seems related to the DX900-EM of 2009, but with the intriguing added abilities of measuring leeway and connecting via Bluetooth to apps (in addition to N2K or 0183 cabled connections). Kees broke the story at METS 2016, and I was part of the SAIL team to award it a Pittman.

AirmarCast_app_screens_with_DX900+_aPanbo.jpgGiven the possibly embarrassing history, I was a little surprised that the DX900+ took a while to ship, but it is now available at outlets like iMarine (and the slick looking iOS AirmarCAST app above is available for download). In fact, occasional Panbo contributor Jeremy Anwyl bought one last summer for his latest vessel — a mighty Nordhavn 76 — and I was hoping to host a dual review with Kees reporting on his DX900+ beta testing experience aboard the awesome sloop Merrimac.

Unfortunately, neither Jeremy nor Kees have reliably working DX900+ sensors yet. It’s not worth getting deep into the details here as both cases are still being investigated by Airmar tech support, but it may be that EM is best suited to simple 12v electronic systems, or maybe that the NMEA 0183 option is preferable because then the power supply can be kept especially clean.

Also, Airmar tells me that numerous DX900+ are out in the field without reported problems, so here’s hoping an owner of this highly innovative sensor will report in about actual results. And that Jeremy and/or Kees will be able to report on working EM sensors soon.


So the ST900/950 ultrasonic speed sensor Kees also reported on at METS 2016 got my “Close but no… cigar” markup mockery because it didn’t actually ship until after Airmar decided that UST800 Smart Sensor and UST850 Smart Sensor titles made more sense. {Correction 2/20: some ST900/950 sensors did ship before the name change.}

I agree that UST800 is a good designation for the ultrasonic version of the ST800, but the best news is that the two UST sensors — the only difference is which standard Airmar casings they fit — are really available. The online prices starting at $918 are not trivial — Airmar does not list retail pricing — but consider this performance graph.


If I understand this graph correctly it shows a boat alternately accelerating and decelerating over about 18 minutes while speed is measured by paddlewheel, ultrasonic, and GPS. The paddlewheel fails quite badly over about 35 knots, but if you click the graph bigger and look closely, you’ll see that the paddlewheel isn’t doing very well at low speeds either.

Moreover, I think it’s safe to presume that Airmar used a clean ST800 or similar paddlewheel sensor for this test, and paddlewheel performance most definitely changes with fouling. Also, note the latency. In acceleration the Ultrasonic usually measures speeds slightly higher than the GPS and paddlewheel and vice versa as the boat slows down, which certainly suggests better responsiveness. But I’d like to see for myself…

Brand new UDST800!


When I asked about testing a UST sensor in January, I was delighted to learn that a UDST would not only be announced soon and was already in production. And, lo, there it is, posing in my shop before I took it down to the boat (and quite like the DST900 Kees saw in 2012).

The UDST800 ultrasonic triducer was also announced early this week — press release PDF here — and though it’s not yet listed at Airmar, here is the combined UDST/UST install guide PDF.

It will be awhile before I actually get to see UDST underway performance in Gizmo, but you can see on the Simrad NSS evo2 screens below that it’s real and ready to go.


Similar Posts:

Maretron ultrasonic wind sensor, the plot thickens
November 14, 2005

Airmar CS4500 Part I (Reliable Boat Speed)
October 5, 2009

Airmar Smart Sensors, lots
September 21, 2005

Ultrasonic Weather Wars, w/ Raymarine as Switzerland
June 23, 2006

Ben Ellison

Ben Ellison

Panbo editor, publisher & chief bottlewasher from 4/2005 until 8/2018, and now excited to have Ben Stein as very able publisher, webmaster, and editing colleague. Panbo is going to the next level in 2019 and beyond.

51 Responses

  1. Henning says:

    I might want to retire my CS4500, in use since 2012 and still in working order, but first I would have to see some satisfied user reports. So I’ll be very interested how a UDST 800 works on Gizmo.
    My CS4500 has quite severe problems with silt in the water like you find in shallow waters with lots of tidal activity (such as the Waddenzee). In these areas, I regularly have crazy readings that swing, in sort of a sinusiodal curve, between about 0.5 knots and 9 knots while going at a steady 6 knots, confirmed by GPS. Each full curve is maybe 20 seconds long. A minute later, with maybe a little less silt in the water, all is back to normal until it starts again a few minutes later. This never happens in clearer water (e.g. not once in 2.000nm of Baltic sailing of last season).
    Another question I have is how fine you can calibrate it. An absolute must for me is ability to apply correction factors for multiple speed levels. In addition to that I would highly appreciate ability to apply different correction factors depending on roll of the boat (port bow or starboard bow). My boat or my install location definitely needs this – and it’s a standard boat and standard install location.
    In theory, the roll-dependent correction should be no problem as there is continuous supply of roll (and tilt) via NMEA 2000 from my H2183 compass.
    The last point, in my opinion, is critical for a sensor like this. It’s targeted at those that badly want precise speed. But the proposition “buy this sensor and you will have breathtakingly accurate speed” is, unfortunately, naive. You need to invest a lot of time in calibration, and, to be able to do that, you need software that allows very fine corrections in a number of different dimensions.
    Otherwise it’s just a sensor that never fouls – also good, of course.

  2. Dan Corcoran (b393capt) says:

    Great Entry, especially the history, it has been a long journey of product announcements. The ability to measure leeway, N2K, and bluetooth access to the sensor being particularly appealing features.
    Over the years it has seemed like two different technologies were being developed by Airmar, the “EM” for example being different from how the CS4500 senses speed through water as described in a detailed product brochure.
    Ben, does the UDST800 and DX900+ have the same guts/technology? Are they the same or different from the CS4500? Can the UDST800 measure leeway and accessed from bluetooth?

  3. Ben Ellison Ben Ellison says:

    No, Dan, just the DX900+ can measure leeway speed/angle and also roll/pitch, as seen in AirmarCAST screens above. It’s also the only transducer with Bluetooth.

  4. Ben Ellison Ben Ellison says:

    Henning, according to the UDST/UST intall guide linked to above, speed calibration is possible, but it’s vague beyond that, dependent apparently on what display you’re using in conjunction. And of course some systems can apply calibration independent of the transducer (but then it only shows up within that system, not to other N2K displays).
    At any rate, this is definitely an interesting and still largely unknown aspect of these speedos. I did check Gizmo’s Maretron DSM to see if it could calibrate the UDST800 like it could the Maretron DST110 (equivalent to Airmar DST800). No dice, but maybe coming in Maretron update?
    Also, I don’t buy that every boat speedo install needs multipoint calibration. I saw good results with Maretron’s calibration, though it did need to be adjusted as paddlewheel got dirty.
    Plus we have not heard about real world results from Airmar’s latest ultrasonic tech. It may look a lot like what Kees saw in 2012 but I gather they’ve working on the Echo Correlation Processor:
    “The UST800/UST850’s echo correlation processor has patented adaptive digital signal processing that automatically adjusts according to boat speed, water depth and water clarity for most accurate speed readup. Reliable operation in both salt and fresh water.”

  5. Francisco says:

    Hi I have tried a DX900 plus plus in my carbon cruiser racer. I had great excitement for it, measuring leeway is a killer app. Unfortunately reality has not met expectations. Speed readings are all over the place. To check power supply issues, I disconnected all electronics and fed it directly from the batteries , reading speed via Bluetooth. Insert far from a marina to limit electromagnetic noise. It does not work I am sorry to report. Can be the carbon hull? Don’t know. Francisco

  6. Ben Ellison Ben Ellison says:

    Thanks for the report, Francisco. An Airmar representative tells me that he thinks “the culprit in this case is the carbon hull” and wonders if you have worked with Airmar tech support?

  7. Crystal Blues Digital says:

    Raymarine sold the CS4500 for a while as a transducer option. We bought one gladly, being fed up with cleaning the paddle wheel transducer. It was installed back in 2003 and is still working, though the temperature probe failed last year. And yes, it wasn’t initially reliable in muddy water, though it always did seem to adapt with time – the Rajand River in Borneo was our haunt for some years. The Raymarine guys tell me they had a bit of trouble with these, and that we’re a lucky boat. So be it. Now I’m hoping for a DX900 for Christmas.

  8. Francisco says:

    Ben. Developing a new electromagnetic sensor, aimed at the racing market, which is incompatible with carbon hulls, seems surprising. I will call airmar support in a few days when I have a bit of time. But the truth is that I have tried it In several conditions, making sure that the level of a electromagnetic noise was low. I was also quite careful to check that the unit was properly inserted in the sleeve. Unless I am proven wrong, I don’t think this product is up to standard for the general public. This may also explain why it was in the making for such a long time after the announcement. Regards

  9. Nick says:

    The Airmar situation over the last decade has been quite surprising, given we had very good and reliable sonic speed devices in 1997.

  10. Ian says:

    Interesting discussion on this subject on Sailing Anarchy:
    from about post #63.
    Maybe the UDST800 isn’t so hot and paddlewheels’ days aren’t over yet?

  11. Compass Marine says:

    What a coincidence that I see this article now. I just got off the phone with tech support regarding a customers failed CS4500 ultrasonic speed unit. It was not a very fulfilling call nor all that reassuring for me to continue installing these.
    What I learned.
    #1 There is no field test for the transducer to confirm whether it is the problem or not.
    #2 There is no repair of the transducer, if it is what failed.
    #3 Other than confirming 12V power at the control box there is no field test to confirm the control box is working.
    #4 There is also most likely no repair to the circuit board (they were not too committal in this) of the CS4500 control box.
    So, I can send it in $$ and they can possibly test it and tell me which part is bad, the transducer or control box, but then they could not confirm availability of parts for this unit. I even gave them the model revision number; 18-449-01 Rev.01
    I have already confirmed it is not the display with a test unit I keep around.
    These ultrasonic sensor kits are very expensive and this one failed for no apparent reason. It’s mounted dry, has remained bone dry, zero corrosion etc. and I have no way to test it nor to even get it repaired. hard to tell a customer whose vintage Data Marine stuff that lasted 31 years that his few year old very expensive Airmar ultrasonic speed unit is dead.
    Obviously I will need to replace it but with what? These new units are not yet proven. If I go to a new unit it will mean a new display too $$$$ as the new ultrasonic units apparently do not send an analog pulse like the CS4500 could..
    Frustrating to say the least.

  12. Ben Ellison Ben Ellison says:

    Always good to hear from you, RC, though what you describe is depressing. I’m hopeful that that “new” UDST/UST transducers and processing boxes are well developed at this point, but some aspects remain mysterious and only time will indicate their reliability.
    For instance, it’s still unclear to me what sort of calibration is possible, and what devices will be able to do it. The Maretron DST110 (sourced from Airmar) that I pulled to try out the UDST800 could be calibrated against SOG and even though it uses a paddlewheel I was able to get a good match between STW and SOG in zero current conditions, and hence fairly good Set/Drift calculations.
    Also I noticed that the Raymarine i70s appears to have multi-point speed calibration for smart speed sensors, as shown in this entry:

  13. Ben Ellison Ben Ellison says:

    I just updated the DX900+ section of this entry to reflect the fact that Jeremy Anwyl’s had been bottom painted, which definitely affects performance and is therefore prohibited in the installation instructions. He will be testing a fresh DX and also a UDST800 (which can be painted).

  14. Jonathan U says:

    Just sent a DX900+ to a client for a new BB&G H5000 install. And as we’ve done on every system for the past decade that requested a sonic sensor, suggested they install an analog paddlehweel prewired into the system for rapid swap if (“when” might be more accurate) the sonic unit fails. I’m optimistic for the DX but history indicates having a backup readily in place is a good move.

  15. Jeremy says:

    Not to add to any confusion, but the bottom paint I applied to the DX900+ is water based and was allowed. (At least according to the owner’s guide I have.) I think Airmar may be updating the manual to state that no bottom paint of any kind should be used, but not sure about this.
    As for the UDST800, I tried one this morning and in brief sea trials can say it looks very encouraging.

  16. LarryR says:

    Hi All, We have two DX900+ units on our 60′ cat and we will be testing them against the ST200’s also installed over the next two regattas in the Caribbean in the next 3 weeks. Any tips you can give me about what to look for. My plan is to use the ST200s into our H5000 to start with and log the data from N2K into Expedition at the same time and compare. I have not calibrated the 900s as yet, in case you have any tips.
    Larry Rosenfeld

  17. peter says:

    Ben, do you know if UDST is (like DX900) dual-axis speed-to-water system or not. European dealer is not able to confirm this.

  18. Ben Ellison Ben Ellison says:

    Sorry but that’s a no, Peter. The UDST outputs the standard set of Depth, Speed through Water, and water Temperature values. By contrast, the DX900 also measures transverse speed, calculates leeway direction, and more. That’s why it sort of needs the Bluetooth app seen up in the entry, at least until some marine instruments learn to display those values:

    • peter says:

      Thank you Ben for information.

      I have noticed PGN 128000 issue already. Also dual-axis STW seems to be a problem for N2K-based MFDs.

  19. Has anyone actually gotten their hands on the UDST? My Airmar DST110 paddlewheel has stopped working again, likely due to junk growing on it, and I would love to know if the UDST actually is something a sailboat should/could use.

    • Keefer Douglas says:

      Seconded! Doesn’t appear to be for sale yet at any of the usual suspects, and Google just returns a link to this article and not much else…

      • Ben Ellison Ben Ellison says:

        The word from Airmar: “​As far as the UDST800, we have been shipping some but they already have a home when we ship them. UDST production is ramping up to a higher level in the next two weeks. ”

        Also, if you have an installer/dealer with a Gemeco account, he or she can probably get one faster than you’ll see them show up in retail channels.

  20. Anyone know if the UDST800 can be mounted inside a fibreglass hull as you could do with many depth sounders? (temperature may be off, but I would expect depth to work… not sure about speed…)

  21. Eliboat says:

    I installed a dx900 in the boat this year. The first one would not transmit depth or temp over the n2k network, but using the app I could see that the transducer was measuring these items, along with leeway, heel, trim etc. Airmar sent a new one to me and everything was transmitted via the network. The problem now is that my speed readings are wildly inaccurate. Yesterday I was tied to a dock on the Piscataqua river and it was reading the current from .8kts up to 5kts. Once underway against the current for the trip home, the Speedo cycled from under a knot to over 9kts. Not only was this clearly wrong, but as my friend who was with me pointed out, had the water speed been changing in that fashion, as quickly as it was, we wouldn’t have been able to stand on the deck without holding on tight to something.
    Not sure what the issue is yet, as I haven’t had a chance to call Airmar.

  22. Tony Dove Tony Dove says:

    Re DX900+

    Interesting … ‘do not anti-foul the transponder face’. :facepalm:

    However … this product seems pretty clearly targeted at (and priced accordingly) the ‘serious’ racers. Serious racers lift their boats and clean, even sand, their hulls before every race … so in the racing season … there wouldn’t be much opportunity for the transponder to foul up.

    Anyway … it comes with a nice flappy-valve gizmo to make withdrawing the transponder at sea easy. So just pull it out … replace with the blanking plug … then clean it … after every time you use the boat. There replace it next time you want to use it.

    If you are using the boat continuously, e.g. cruising, just make it a daily ritual to pull, clean, replace.

    So I don’t see the ‘do not anti-foul the transponder face’ edict as much of an issue, really. :thumb:

    The reports of widely variable readings is more of a concern. :banghead: Those same ‘serious’ racers would not take kindly to paying that much for something that is unreliable. The sooner Airmar sort out this issue … the better.

  23. Robert Settle says:

    I’ve been awaiting a report on the UDST that arrived on Gizmo. It’s a revolutionary product if it actually owns up to it’s claims. It’s been a while since the review and the product is shipping and is stocked well. I’m about to pull the trigger on this one. There is a real scarcity of real world info re. this transducer on the web. So far Panbo is the only one that has a report on this. I’m a full time cruising sailor and the idea of not having to think about a paddlewheel -ever again is one that is worth the cost of this transducer. But is it still beta ware?

    • Ben Ellison Ben Ellison says:

      Hi Robert, I’m sorry to report that my UDST testing is still unresolved. The problem I’ve experienced — consistent and proportional high readings — may be due to the transducer but is much more likely the result of the installation.

      When I briefly hauled Gizmo very soon after leaving her winter berth, I noticed that the UDST face was set back about 1/4-inch from flush with the casing’s outer end. The casing is about 20 years old and originally housed a Datamarine sensor, but I believe it to be standard Airmar so I let it go until I started to see apparent high readings in areas where STW should have been very close to SOG. I did fiddle with the UDST’s fixing ring so it would sit deeper in the casing — some wet fun with the boat in the water — but saw no improvement and I have not yet hauled the boat again. (I was planning to about now, but recently decided on another winter afloat partially so that I can continue other testing.)

      What I should have done, and will now, is to ask Airmar for guidance. So thanks for the motivation and sorry to play an old guy who has accumulated far too much stuff to test quickly or efficiently. By the way, the UDST has performed fine in every other way, and I suspect that if I could calibrate it, even simply with a single percent type correction, it would be spot on. And I have lots of logged NMEA 2000 data logs might support that theory, though I have not looked at them yet 😉

  24. Eliboat says:

    Well, I’m still trying to get it working properly. Calibrating the transducer is a bit of a black art, and I was never able to get stAble speed readings. Depth, temperature and heel angle have been fine. I will continue to work with it next season, but if I can’t get it sorted, then I’ll go back to a paddle wheel.

    • Ben Ellison Ben Ellison says:

      Hi Eliboat, I believe from your June comment that you have DX900, not the UDST that Robert Settle just asked about. I’m sure I’m not the only who would like to hear more about your experience when possible, but the two transducers have gotten a little mixed up in this thread though they are very different.

  25. Anonymous says:

    Whoops! My bad. Yes two different technologies.

  26. Keefer Douglas says:

    I tracked down and installed a UDST recently. Boat is still on the hard and will be until Spring, so cannot comment yet on calibration or other issues. However, I noticed that even using the casing provided by Airmar with the new transducer, I too have the same 1/4 inch gap between the face of the transducer and the outer edge of the casing.

    Would prefer not to have to change out the casing again if there is another solution to get it flush (assuming that is indeed the cause of the speed issues noted above)!

    • Ben Ellison Ben Ellison says:

      Thanks so much for speaking up, Keefer, though your experience may indicate that I made a wrong assumption about the transducer fit being the problem. I have already written to Airmar and also found this in the Ultrasonic Processor manual (which was updated since my install):

      “If the speed reading is consistently the same percentage higher
      or lower than the true speed, the speed function within the
      instrument needs to be re-calibrated. Follow the instructions in
      your instrument owner’s manual.”

      I’d rather calibrate the processor itself so that all instruments (and other devices that can use or display STW) would get the same data, but there may well be instruments that can apply a percentage correction that shows on their screens and maybe within their brand network. Maybe someone has a suggestion (and I will try to check out myself). Offhand, I recall that some Simrad, B&G and Furuno displays can apply corrections to some common N2K values.

  27. Ben Ellison Ben Ellison says:

    Cool: Sounds like my UST800 testing issue is simply about calibration and that several options are in the works:

    “Here’s where we are in this product as it pertains to calibration. As you know, our OEM partners have a long integration period to incorporate the products into their system. Once that is done, users will have a quick way to do multipoint calibrations on the UDST and DX products through their on board electronics. In much shorter time than that, we are in the final test stages for a new bit of PC software which will allow for those products and any other Smartsensor to quickly and easily be calibrated. Those calibrations will be stored in the device and will push corrected data to the network/instruments. I’m being told that it will be ready by years’ end. ”

    Note that this applies to the DX transducer too, but also that my Airmar contact joked about how their developers did not specify which “years’ end” 😉

    • Keefer Douglas says:

      So it will be as simple as linking a PC running this software into the N2K network? My new system will have a USB-enabled XB-6000 AIS transponder that I gather ports N2K data to a PC. But will this be capable of routing the signal in the other direction, going from PC to UDST? Or will I need a different sort of link?

      • Ben Ellison Ben Ellison says:

        Sorry, Keefer, but it probably won’t be that easy. The ability of your Vesper Smart AIS to put more data than AIS out over USB and WiFi is great, but it’s limited to common navigation fields because translation is involved. This software will likely require a full-on PC-to-N2K gateway like the Airmar U200, though the Actisense NGT-1 may also work.

        But I’m not sure you should worry about calibration until you try your install. I don’t think that my boat hull or the location of the UDST are weird, but it is one of the first units off the production line, I think.

        • Keefer Douglas says:

          Thanks Ben, much appreciated. Nothing’s ever quite so simple as we might hope it to be, eh? I will post an update re: need for calibration (or lack thereof) once the boat is wet and the system is up and running…

  28. Robert Settle says:

    Thanks Ben and Keefer for your input from real-world use. Hmmm. So even with the provided Airmar housing installed the instrument face is not sitting flush with the hull? I would assume this is a major problem with the ultrasonic sensor. Water flow needs to be across the face and sitting short it would create a burble on the sensor face and create inacuracies I would assume. Unrelated Anecdotal evidence about Airmar from a fellow cruiser here in the Sea of Cortez -he says he has had 2 failures of the dst800 and now keeps a spare “just in case”…
    Regardless I see myself buying the WS300 and the UDST800 and just crossing my fingers. I will haul soon and hope I can “McGuyver” any issues with the installation of the housing and sensor flush with the hull. My current location for my paddlewheel is in front of the keel (Norseman 447) and accessing it from inside requires tossing the forepeak, removing a shelf, two drawers, and a floor panel. My issue with paddlewheels is they go innacurate quite quickly after cleaning. Just a couple days. First is a slime layer quickly followed by hard growth. So they are basically useless unless maintained weekly. Who needs innacurate data? For me it’s unthinkable to toss the forepeak every time I want good speed data which is always. I have a B&G Zeus3 and heading sensor w/4G Radar -good speed data will make the whole system work with their sailing software.

  29. San Diego sailor says:

    So what is the consensus? Do I buy a UDST800 with some confidence? I am a typical cruiser / racer.

    • Ben Ellison Ben Ellison says:

      Well, as discussed in the November comments above, the UDST800 I’m testing is consistent and reliable, but I’m really looking forward to a means of calibrating the readings that is supposedly in the works.

      • Ian says:

        I have been watching this conversation with interest. We sail in an area with strong tidal flow – and picking your time and exposure can be quite critical.

        I went through the misery of trying to adapt a late model Garmin GST43 transducer to a Raymarine N2k system – ended up being an expensive (time and parts) nightmare – that ultimately didn’t work or couldn’t be properly calibrated. Nice try = no cigar.

        has there been any further developments – or are we still in a state of limbo with Airmar – promising, promising but yet to deliver?

        • Ben Ellison Ben Ellison says:

          Hi Ian, I contacted Airmar and progress is being made. They have a PC program that works alongside their WeatherCaster software and can “find a DST800/UDST800/DX900 connected to the network and allow speed calibration, depth offset, depth calibration, temperature offset, and output filtering to be programmed and saved to the sensor.”

          That means an Airmar or Actisense NGT-1 PC-to-NMEA 2000 bridge is needed to run the software, but I hope to try it soon. Also, it’s not yet available to the public, though apparently it is being distributed by Gemeco to technical dealers.

          The calibration will also be added to Airmar’s CAST app eventually, but that’s only relevant to DX900 owners as it includes a Bluetooth radio.

          • Ian says:

            Thanks Ben
            I watch with interest – I am a little amazed with Airmar – their marketing hype isnt even close to matching what is out in the market. My tech guy ( a first principles devotee) is also a little bemused at marketing get ahead of the actual product promised performance. the read on the situation is its still pretty much a beta product for recreational yachties/ boaties.

  30. Keefer Douglas says:

    I now have the boat in the water and have fired up the electronics. The UDST 800 gave me a depth reading of 3.5 feet (from the top of the keel where the thru hull is), and I measured 5.5 feet via lead line. Boat draws about 5 even and the keel is roughly 3 – 3.5 of that, so it is already pretty close without any calibration. Assuming readings stay consistent I will likely set an offset via the instruments and call it good enough. Have not had a chance to leave the slip and test out speed yet. Will report back again when we get out on the water.

    • Keefer Douglas says:

      After a completely lost season (engine issues), we finally got out on the water today for the first actual test of the instruments. Happy to report that the UDST 800 worked perfectly. Read 4.8 feet in the slip today, which is almost exactly what I would expect a true reading to be from the position of the transducer with no offset. While motoring around Rockhold Creek and Herring Bay on the Chesapeake, depth readings aligned with expectations for the waters we traversed, and speed through the water matched up reasonably well with SOG from the GPS (no way to judge current, but winds were calm and seas flat).

  31. Palio says:

    I gather from the foregoing that the Airmar UST800 is still not ready for prime time. Raymarine says that the unit will pass data to a Raymarine display, but at the moment, there is no way to calibrate. I’m curious to know how it might do in a situation like mine – a brown water, tidal creek infested area, like South Carolina. Any thoughts, observations?

    • Ben Ellison Ben Ellison says:

      As best I know, no third party display can yet directly calibrate a UST800/850 or UDST800. Some may be able to apply corrections to the output, but that’s not the same thing. Also, judging from Airmar’s download page, the calibration possible via WeatherCaster is not available to the public:

      I will ask about this at METS.

      • Maddox says:

        When I go to the software download link you provided, I did not see any restriction about calibration for WeatherCaster?

        Also, did you get a chance to ask at METS? Thanks,

        • Ben Ellison Ben Ellison says:

          Hi Maddox, as I commented about last April, WeatherCaster apparently needs a patch program in order to calibrate a UDST800. And that patch does not yet seem to available to the public.

          However, I failed to make contact with Airmar at METS and have been poor at following up on this issue overall. I apologize, and am putting it at the top of my list.

  32. Maddox says:

    I have the DST800 and would like to use the UDST800. Does the UDST800 use the same housing as the DST800 or do I have to haul and replace/install a new housing?

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